Football is fun for bickering, but for really wrecking family dinners over the Thanksgiving holidays, try tackling the week’s political argument over the age of the Earth. The fun kicked off when GQ Magazine quoted political hot property Sen. Marco Rubio, R-Fla. But Rubio’s answer upset pundits and geophysicists. The actual age of our planet had been provided some time ago by a scientist whose contributions were ignored in the opinion-page fights that followed. The scientist was Caltech geophysicist, Clair Cameron Patterson , the forgotten man in the week’s most discussed debate, besides Thursday’s Lions vs. Texans NFL refereeing debacle , of course.
Scientist of the Day – Clair Patterson
Both isotopes are the starting points for complex decay series that eventually produce stable isotopes of lead. Uranium-lead dating was applied initially to uranium minerals, e. The amount of radiogenic lead from all these methods must be distinguished from naturally occurring lead, and this is calculated by using the ratio with Pb, which is a stable isotope of the element then, after correcting for original lead, if the mineral has remained in a closed system, the U: Pb and U: Pb ages should agree.
If this is the case, they are concordant and the age determined is most probably the actual age of the specimen. If the ages determined using these two methods do not agree, then they do not fall on this curve and are therefore discordant.
Lead isochrons are also an important radioactive dating process. Note that This data is reproduced from Dalrymple, The Age of the Earth. * Note that 40K also.
Dating , in geology , determining a chronology or calendar of events in the history of Earth , using to a large degree the evidence of organic evolution in the sedimentary rocks accumulated through geologic time in marine and continental environments. To date past events, processes, formations, and fossil organisms, geologists employ a variety of techniques. These include some that establish a relative chronology in which occurrences can be placed in the correct sequence relative to one another or to some known succession of events.
Radiometric dating and certain other approaches are used to provide absolute chronologies in terms of years before the present. The two approaches are often complementary, as when a sequence of occurrences in one context can be correlated with an absolute chronlogy elsewhere. Local relationships on a single outcrop or archaeological site can often be interpreted to deduce the sequence in which the materials were assembled.
This then can be used to deduce the sequence of events and processes that took place or the history of that brief period of time as recorded in the rocks or soil. For example, the presence of recycled bricks at an archaeological site indicates the sequence in which the structures were built. Similarly, in geology, if distinctive granitic pebbles can be found in the sediment beside a similar granitic body, it can be inferred that the granite, after cooling, had been uplifted and eroded and therefore was not injected into the adjacent rock sequence.
How Science Figured Out the Age of Earth
All rights reserved. Zircon crystals from the Jack Hills of Australia, like the one above, reveal that continents arose just million years after our solar system formed, much earlier than previously thought. Australia holds the oldest continental crust on Earth, researchers have confirmed, hills some 4.
Calculations of Earth’s age using radioactive decay showed that Earth is Uranium-lead dating can be used to date igneous rocks from 1 million years to.
In , shortly after the discovery of radioactivity , the American chemist Bertram Boltwood suggested that lead is one of the disintegration products of uranium, in which case the older a uranium-bearing mineral the greater should be its proportional part of lead. Analyzing specimens whose relative geologic ages were known, Boltwood found that the ratio of lead to uranium did indeed increase with age.
After estimating the rate of this radioactive change, he calculated that the absolute ages of his specimens ranged from million to 2. Though his figures were too high by about 20 percent, their order of magnitude was enough to dispose of the short scale of geologic time proposed by Lord Kelvin. Versions of the modern mass spectrometer were invented in the early s and s, and during World War II the device was improved substantially to help in the development of the atomic bomb.
Soon after the war, Harold C. Urey and G. Wasserburg applied the mass spectrometer to the study of geochronology. This device separates the different isotopes of the same element and can measure the variations in these isotopic abundances to within one part in 10, By determining the amount of the parent and daughter isotopes present in a sample and by knowing their rate of radioactive decay each radioisotope has its own decay constant , the isotopic age of the sample can be calculated.
For dating minerals and rocks, investigators commonly use the following couplets of parent and daughter isotopes: thorium—lead, uranium—lead, samarium—neodymium, rubidium—strontium, potassium—argon, and argon—argon The SHRIMP Sensitive High Resolution Ion Microprobe enables the accurate determination of the uranium-lead age of the mineral zircon, and this has revolutionized the understanding of the isotopic age of formation of zircon-bearing igneous granitic rocks.
NSF pushed to boost funding for dating and squeezing rocks
Earth’s magnetic field periodically reverses such that the north magnetic pole becomes the south magnetic pole. The latest reversal is called by geologists the Matuyama-Brunhes boundary MBB , and occurred approximately , years ago. The MBB is extremely important for calibrating the ages of rocks and the timing of events that occurred in the geological past; however, the exact age of this event has been imprecise because of uncertainties in the dating methods that have been used.
The team studied volcanic ash that was deposited immediately before the MBB. This volcanic ash contains small crystals called zircons.
Uranium-lead dating computes the age of the earth at billion years old with less than 1% margin of error. It is one of the oldest and most.
He later received his Ph. In collaboration with George Tilton , Patterson developed the uranium—lead dating method into lead—lead dating. By using lead isotopic data from the Canyon Diablo meteorite , he calculated an age for the Earth of 4. Patterson had first encountered lead contamination in the late s as a graduate student at the University of Chicago. His work on this subject led to a total re-evaluation of the growth in industrial lead concentrations in the atmosphere and the human body, and his subsequent campaigning was seminal in the banning of tetraethyllead in gasoline and lead solder in food cans.
Clair Cameron Patterson was born in Mitchellville, Iowa.
How is Earth’s Age Calculated?
Lead isotopes are commonly used in dating rocks and provide some of the best evidence for the Earth’s age. In order to be used as a natural clock to calculate the age of the earth, the processes generating lead isotopes must meet the four conditions of a natural clock: an irreversible process, a uniform rate, an initial condition, and a final condition. Dalrymple cites examples of lead isotope dating that give an age for the earth of about 4.
Lead isotopes are important because two different lead isotopes Pb and Pb are produced from the decay series of two different uranium isotopes U and U. Since both decay series contain a unique set of intermediate radioactive isotopes, and because each has its own half-life, independent age calculations can be made from each Dalrymple
Dating meteorites thus allows us to give a lower age to the Solar System (4,56 billion years old). Solar System. Lead isotope isochron that Clair Patterson used.
The first of these methods is wrong in principle and yields results which are internally in-consistent and widely at variance both with my own solutions 3,4 and with known geochemical data. The second is sound in principle and leads to results consistent with mine ; but it is wrongly stated by Jeffreys, and the solitary example given is arithmetically incorrect.
Clair Cameron Patterson
Radiometric dating finds Earth is 2. This amazing fact seemed like alchemy to many, but American chemist Bertram Borden Boltwood was intrigued. Boltwood studied this concept of “radioactive series,” and found that lead was always present in uranium and thorium ores. He believed that lead must be the final product of the radioactive decay of uranium and thorium.
A few years later, in , he reasoned that since he knew the rate at which uranium breaks down its half-life , he could use the proportion of lead in the uranium ores as a kind of meter or clock. The clock would tell him how long that ore — and by extension, the earth’s crust — had existed.
By dating the rocks in Earth’s ever-changing crust, as well as the rocks measured ratios of lead isotopes in samples of the meteorite that put.
Uranium-lead dating computes the age of the earth at 4. It is one of the oldest and most refined radiometric dating schemes, with a routine age range of about 1 million years to over 4. The method relies on the coupled chronometer provided by the decay of U to Pb, with a half-life of 4. One of the advantages of uranium-lead dating is the two separate, chemically identical chronometers and is accepted as the most reliable measurement of the age of the Earth.
Loss leakage of lead within the sample will result in a discrepancy in the two decay schemes, resulting in a different age determined by each decay scheme. This effect is referred to as discordance, and provides a check on the reliability of the age. The presence of minerals or zones within minerals, older than the rock being dated can also cause age-discordance. In either case, the geochronologist is warned that such uranium-lead ages cannot be taken at face value.
When such discordant ages are encountered, a suite of several samples must be analyzed, and one of several mathematical methods, depending on the nature and complexity of the age discordance, applied to arrive at a reliable age-estimate. Uranium-lead dating is usually performed on the mineral zircon ZrSiO4 , though it can be used on other minerals such as monazite, titanite, and baddeleyite. Zircon incorporates uranium and thorium atoms into its crystalline structure, but strongly rejects lead.
Zircon is very chemically inert and resistant to mechanical weathering — a mixed blessing for geochronologists, as zones or even whole crystals can survive melting of their parent rock with their original uranium-lead age intact. Zircon crystals with prolonged and complex histories can thus contain zones of dramatically different ages, usually, with the oldest and youngest zones forming the core and rim, respectively, of the crystal.
He hardly knows which is which.